Photograph courtesy Philadelphia Commercial Museum
THE HOLD OF A LAKE STEAMER WHICH BRINGS TIIE ORE FROM ITHEIMINES OF
MINNESOTA TO THE STEEL INDUSTRY OF PENNLANI)
The huge buckets can scoop up two 4-horse wagon-loads of ore at a time.
In some plants the packing machinery is
far from the least interesting part of the
equipment. Leading from the bin is a
large hopper with an automatic weighing
machine. The barrel, with the head in
place, but having a two or three-inch hole
in the center, is put in position, a big fun
nel connecting the head-bung with the
hopper. Through this the cement flows
until both the barrel and the funnel are
full.
The barrel is then lifted away by a ma
chine and set on a mechanism that may
be depended on to pack the cement tight.
Overhead is a shaft made on the prin
ciple of that which drives the pistons of
an automobile engine. As it turns around,
it lifts the barrel several inches, and then
lets it drop, repeating the process about
as rapidly as one can count. When this
shaking process is finished all of the ce
ment has been driven out of the funnel
and into the barrel, which is now packed
as tightly as if it were solid rock. A piece
of wood is nailed over the hole, and the
steel-hooped barrel, weighing nearly four
hundred pounds, is ready to be trans
ported.
With three separate operations of con
verting hard solids of considerable size
into dust, at the rate of thousands of bar
rels a day, one would naturally think of
a cement plant as the dustiest ,place in all
the world. Yet in many modern Port
land cement plants there is not as much
free dust floating around as one finds in
the average old-fashioned country grist
mill. Indeed, there are some plants so
free from dust that one might go through
them in a dress suit and come out with
out serious need of a whisk-broom or a
clothes-brush.
The shearing strength of concrete made
from Portland cement is rising to such
unexpected heights that the experts sug
gest that the day may not be far distant
when architectural specifications will per
mit the same lightness of construction
that is accepted with steel. A world
shortage of steel might be compensated